The Synergistic Effects of High Nitrate Concentrations on Sediment Bioreduction

Thorpe, Clare L.; Law, Gareth T. W.; Boothman, Christopher; Lloyd, Jonathan R.; Burke, Ian T.; Morris, Katherine

doi:10.1080/01490451.2011.581332

Cited by 28 publications

(21 citation statements)

References 56 publications

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“…Analysis of the bacterial community in the oxic starting sediment revealed a relatively diverse community with 16 phyla detected through pyrosequencing of 16S rRNA gene amplicons. Communities were dominated by species representing the acidobacteria (47%) and proteobacteria (32%), a finding consistent with previous studies conducted on Sellafield-type sediments (38,39). Of the most dominant individual species, an uncharacterized acidobacterium and a bacterium of the Bradyrhizobiaceae family (proteobacteria) represented 5 and 4% of the complex microbial community, respectively.…”

Section: Resultssupporting

confidence: 77%

“…This site was selected because our group has extensive experience studying the biogeochemistry of sediment from this area. Samples were collected from the shallow subsurface at a locality ϳ2 km from the Sellafield site, in the Calder Valley, Cumbria (38)(39)(40). Samples were transferred to sterile containers, sealed, and stored in the dark at 4°C prior to use.…”

Section: Methodsmentioning

confidence: 99%

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The Impact of Gamma Radiation on Sediment Microbial Processes

Brown

Boothman

Pimblott

et al. 2015

Appl Environ Microbiol

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cMicrobial communities have the potential to control the biogeochemical fate of some radionuclides in contaminated land scenarios or in the vicinity of a geological repository for radioactive waste. However, there have been few studies of ionizing radiation effects on microbial communities in sediment systems. Here, acetate and lactate amended sediment microcosms irradiated with gamma radiation at 0.5 or 30 Gy h ؊1 for 8 weeks all displayed NO 3 ؊ and Fe(III) reduction, although the rate of Fe(III) reduction was decreased in 30-Gy h ؊1 treatments. These systems were dominated by fermentation processes. Pyrosequencing indicated that the 30-Gy h ؊1 treatment resulted in a community dominated by two Clostridial species. In systems containing no added electron donor, irradiation at either dose rate did not restrict NO 3 ؊ , Fe(III), or SO 4 2؊ reduction. Rather, Fe(III) reduction was stimulated in the 0.5-Gy h ؊1 -treated systems. In irradiated systems, there was a relative increase in the proportion of bacteria capable of Fe(III) reduction, with Geothrix fermentans and Geobacter sp. identified in the 0.5-Gy h ؊1 and 30-Gy h ؊1 treatments, respectively. These results indicate that biogeochemical processes will likely not be restricted by dose rates in such environments, and electron accepting processes may even be stimulated by radiation. In many countries, including the United Kingdom, the current policy for the long-term disposal of intermediate-level radioactive waste is to a deep geological disposal facility (GDF). In UK disposal concepts for higher-strength rocks and lower-strength sedimentary rocks, much of the intermediate-level radioactive waste is immobilized with a cementitious grout in stainless steel containers that are then surrounded with a cementitious backfill prior to closure of the facility (1). The vicinity of a GDF will not be a sterile environment, and microbial activity in the surrounding geosphere could have important implications for the evolution of biogeochemical processes, including microbial gas generation and utilization, microbially induced corrosion of waste containers and contents, and the mobility of radionuclides (2). In addition, there will be elevated concentrations of potential electron donors in and around the repository, including organics from the degradation of cellulose in the waste (3), and also molecular hydrogen from the radiolysis of water and the anaerobic corrosion of steel drums (4). Indeed, the availability of alternative electron acceptors will likely not be limited, since nitrate can be present in nuclear waste materials (5), and Fe(III) will be present due to aerobic corrosion of waste components and engineered infrastructure during the operational phase of the GDF.The stimulation of an Fe(III)-reducing community due to an increase in electron donors and acceptors is of particular interest since this may promote the reduction and precipitation of redoxactive radionuclides via the production of biogenic Fe(II)-bearing phases (2, 6). Indeed, many key Fe(III)-reducin...

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Section: Resultssupporting

confidence: 77%

Section: Methodsmentioning

confidence: 99%

The Impact of Gamma Radiation on Sediment Microbial Processes

Brown

Boothman

Pimblott

et al. 2015

Appl Environ Microbiol

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“…and Ochrobactrum sp. from the radioactively contaminated sediment with high nitrate concentration (Thorpe et al, 2012) and Sulfuricurvum sp. and Desulfovibrio sp.…”

Section: Discussionmentioning

confidence: 99%

Elevated nitrate enriches microbial functional genes for potential bioremediation of complexly contaminated sediments

et al. 2014

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Nitrate is an important nutrient and electron acceptor for microorganisms, having a key role in nitrogen (N) cycling and electron transfer in anoxic sediments. High-nitrate inputs into sediments could have a significant effect on N cycling and its associated microbial processes. However, few studies have been focused on the effect of nitrate addition on the functional diversity, composition, structure and dynamics of sediment microbial communities in contaminated aquatic ecosystems with persistent organic pollutants (POPs). Here we analyzed sediment microbial communities from a field-scale in situ bioremediation site, a creek in Pearl River Delta containing a variety of contaminants including polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs), before and after nitrate injection using a comprehensive functional gene array (GeoChip 4.0). Our results showed that the sediment microbial community functional composition and structure were markedly altered, and that functional genes involved in N-, carbon (C)-, sulfur (S)-and phosphorus (P)-cycling processes were highly enriched after nitrate injection, especially those microorganisms with diverse metabolic capabilities, leading to potential in situ bioremediation of the contaminated sediment, such as PBDE and PAH reduction/degradation. This study provides new insights into our understanding of sediment microbial community responses to nitrate addition, suggesting that indigenous microorganisms could be successfully stimulated for in situ bioremediation of POPs in contaminated sediments with nitrate addition.

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“…Sediments representative of the Quaternary unconsolidated alluvial flood-plain deposits that underlie the UK Sellafield reprocessing site were collected from the Calder Valley, Cumbria, from a well characterised field site Thorpe et al 2012). Sediments were transferred directly into sterile containers, sealed, and stored at 4 C prior to use.…”

Section: Sedimentmentioning

confidence: 99%

Retention of^99mTc at Ultra-trace Levels in Flowing Column Experiments – Insights into Bioreduction and Biomineralization for Remediation at Nuclear Facilities

Thorpe

Lloyd

Law

et al. 2016

Geomicrobiology Journal

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The behavior of technetium at ultra-trace (<10 ¡10 mol l ¡1 ) concentrations in bioreducing sediment column experiments was investigated using 99m Tc g-camera imaging. Four flowing sediment columns were biostimulated for varying periods of time, using acetate as an electron donor, such that on the day of imaging they represented oxic, early metal-reducing, Fe(III)-reducing and sulfate-reducing conditions. Prior to imaging, columns were spiked with 9.6 MBq of 99m Tc(VII)O 4 ¡ , which is relevant to the 99 Tc mass concentrations observed at nuclear facilities, run under site relevant flow conditions, and imaged using g-camera imaging at 20 min intervals over 12h. In the oxic column 99m Tc behaved as a conservative tracer and did not interact significantly with the sediment. In all of the biostimulated columns 99m Tc associated with the sediment although the spike was least mobile in the order sulfate < Fe(III)-reducing < early metal-reducing columns, confirming higher reactivity for 99m Tc under increasingly reducing conditions. Columns were destructively sampled after 99m Tc decay (5 days storage), and 0.5 N HCl extractable Fe as Fe (II) was measured at 2 cm intervals along the column length. The Fe(II) measured in all electron donor amended columns was present in stoichiometric excess to the 99m Tc. Geochemical modelling and aqueous geochemical data from the different biostimulation treatments suggested that the elevated pH observed in the more reduced columns lead to increased sorbed and mineral associated Fe(II), both stronger reductants for Tc(VII) than aqueous Fe(II). In the sulfate reduction column the presence of FeS lead to the fastest rates of 99m Tc immobilization. The results are the first to show the variable but significant retention of 99m Tc at ultra-trace levels relevant to conditions at many nuclear sites in a range of biostimulated sediment columns and present a positive outlook for the treatment of 99 Tc contaminated groundwater through in-situ biostimulation.

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The Synergistic Effects of High Nitrate Concentrations on Sediment Bioreduction

Cited by 28 publications

References 56 publications

The Impact of Gamma Radiation on Sediment Microbial Processes

The Impact of Gamma Radiation on Sediment Microbial Processes

Elevated nitrate enriches microbial functional genes for potential bioremediation of complexly contaminated sediments

Retention of^99mTc at Ultra-trace Levels in Flowing Column Experiments – Insights into Bioreduction and Biomineralization for Remediation at Nuclear Facilities

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The Synergistic Effects of High Nitrate Concentrations on Sediment Bioreduction

Cited by 28 publications

References 56 publications

The Impact of Gamma Radiation on Sediment Microbial Processes

The Impact of Gamma Radiation on Sediment Microbial Processes

Elevated nitrate enriches microbial functional genes for potential bioremediation of complexly contaminated sediments

Retention of99mTc at Ultra-trace Levels in Flowing Column Experiments – Insights into Bioreduction and Biomineralization for Remediation at Nuclear Facilities

Contact Info

Product

Resources

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Retention of^99mTc at Ultra-trace Levels in Flowing Column Experiments – Insights into Bioreduction and Biomineralization for Remediation at Nuclear Facilities